Gating system for introducing additives to molten metal

ABSTRACT

A gating system which includes a treating basin for treating molten metal such as cast iron with additives such as a nodularizing agent. Molten metal is introduced into the basin by way of a passage such as a downsprue and from the basin to a mold cavity by way of a passage such as runner bars and ingates. A restriction (dam gate) is provided in the last mentioned passage and controls the dwell time of molten metal in the treating basin. An additive reservoir is connected with the treating basin and a closure is provided which temporarily restrains flow from the basin.

United States Patent 191 Moore et al.

[ GATING SYSTEM FOR INTRODUCING ADDITIVES TO MOLTEN METAL [75]Inventors: William H. Moore, Purchase, N.Y.;

Harry H. Kessler, Ladue, Mo.

[73] Assignee: Meehanite Metal Corporation, White Plains, NY.

[22] Filed: Feb. 4, 1971 [21] Appl. No.: 112,553

[52] US. Cl... 164/363, 164/362, 164/358, 164/55, 164/57, 164/80,164/133, 164/134 [51] Int. Cl. B22c 9/08 [58] Field of Search.....,164/358, 362, 359, 164/363, 55, 80, 72, 133, 360, 134

[56] References Cited UNITED STATES PATENTS 1,664,452 4/1928 Daniels etal. 164/358 362,337 3/1887 Walker 164/362 1,239,586 9/1917 Gebhard164/359 1,410,775 3/1922 Thomas 164/363 X 257,558 5/1882 Cross et al.164/359 277,131 5/1883 Harrison 164/362 508,884 11/1893 James 164/3622,247,777 7/1941 Hagemeycr 164/133 X [4 1 Jul 17, 1973 OTHERPUBLICATIONS Gating of Ductile Iron Castings," by R. W. White, FoundryFeb. 1960, pp. 101-407. Principles of Gating by Wallace, J. F. andEvans, E. B., Foundry, Oct. 1959, pp. 74-81.

Primary Examiner-J. Spencer Overholser Assistant Examiner-V. K. RisingAtt0rneyWoodling, Krost, Granger & Rust [57] ABSTRACT A gating systemwhich includes a treating basin for treating molten metal such as castiron with additives such as a nodularizing agent. Molten metal isintroduced into the basin by way of a passage such as a downsprue andfrom the basin to a mold cavity by way of a passage such as runner barsand ingates. A restriction (dam gate) is provided in the last mentionedpassage and controls the dwell time of molten metal in the treatingbasin. An additive reservoir is connected with the treating basin and aclosure is provided which temporarily restrains flow from the basin.

7 Claims, 5 Drawing Figures Patented July 17, 1973 3,746,078

2 Sheets-Sheet 1 INVENTORS 7 WILL/AM H. MOORE BY HARRY H. KESSLERPatented July 17, 1973 3,746,078

2 Sheets-Sheet 2 INVENTORS WILLIAM H. MOORE BY HARRY H. KESSLER GATINGSYSTEM FOR INTRODUCING ADDITIVES T MOLTEN METAL Our invention relates toinoculation of cast iron in the mold during the pouring operation. Itrelates, also, to a method of alloy or other addition to the metalduring the casting operation and, more particularly, to the addition ofvolatile alloys during the casting operation.

It has been realized for some time that the inoculation of cast iron forthe purpose of graphitizing or nodularizing or both is not a permanenteffect and tends to decrease in intensity of effect as the metal is heldfor some time in the ladle before casting. To overcome this fadingeffect, it has been proposed that inoculation be conducted in the moldor in the ladle during the actual pouring operation. Methods ofaccomplishing this late inoculation, well known to those skilled in theart, involve the addition of alloy in the gating system during pouring,the placement of alloy in the gating system prior to casting and otherdevices-such as rods or bars of inoculant material immersed in thestream of molten metal during the pouring operation. These methods areinclined to be non-uniform in practice and I do not act equallyeffectively during the complete pouring cycle of a given casting.

Our invention has, for its object, an improved controllable method ofinoculating in the mold during casting.

Another object is to provide an improved gating system for addingmaterials to molten metal during pouring of the same into a mold.

Another object is the freedom from smoke and fume during the inoculatingprocedure.

Another object is the cleaning of the inoculated metal during casting,so as to provide a casting free of dross and inclusions.

Another object is the more efficient use of volatile inoculant byprevention of oxidation during the inoculating procedure.

Another object is to eliminate the fading of inoculating effect duringthe handling and casting of the metal.

Other objects of our invention will be apparent from the specificationand drawings in which:

FIG. I is a schematic isometric view of the preferred gating system ofthis invention without the mold material such as sand being shown, inwhich:

1 is a downsprue for receiving molten metal,

2 is a runner connecting with 3 a basin or dam area,

4 is an alloy reservoir,

6 is the position a skimmer or strainer will occupy in the finished moldwhich in this instance will be shown as sand and the skimmer will alsobe of sand,

7 is a constricted opening or darn gate area having an area related tothe flow rate of metal,

8 is a runner bar,

9 is an ingate to the casting,

10 is the casting or mold cavity, and

11 is the position of a consumable closure for the basin or dam area 3in the mold prior to the pouring of molten metal;

FIG. 2 is an elevational view of the basin and alloy reservoir sectionof the mold in which:

4 is the reservoir containing alloy 12 to be added and closed at itsupper end with sand,

6 is a skimmer placed just downstream of the basin,

7 is the dam gate area comprising a constricted passage having thesmallest area in the system and related to the desired pouring rate,

8 is the runner bar leading to the casting 10 via ingate 9 and,

11 is a consumable closure for the basin or darn area FIG. 3 is afragmentary view similar to FIG. 1 but showing a modification in which:

15 is an alloy reservoir similar to reservoir 4 but is located below thedam area or basin 3;

FIG. 4 is a fragmentary view similar to FIGS. 1 and 3 but showing amodification in which:

17 is an alloy reservoir similar to reservoirs 4 and 15 but is locatedahead of the dam area or basin 3; and

FIG. 5 is an isometric view of the dam area or basin 3 prior to thepouring of molten metal, in which:

l9 and 21 are consumable polystyrene members placed longitudinally inthe basin to provide increased metal flow channels, in this instancethree in number 22, 23 and 24. In this embodiment it is preferred thatthe molten metal enter from the left end or the basin as viewed in thisdrawing but it is not absolutely necessary.

Our mold treatment system comprises essentially three parts, vix., ameans of metal entry to a dam gate and from the dam gate to the casting,a polystyrene or other consumable support or closure for a darn area orbasin, a dam gate and a dam area or basin where the alloy reaction takesplace and where slag, dirt, dross or oxides from the alloy reaction isconfined to this area by means of a strainer or other skimming device.

One function of the dam area is to provide a pool of metal to give timefor the inoculation to take place. To make this possible we like to havea total volume in the dam area and to provide a dam gate size so as toprovide between 1 second and 2 seconds treatment time for the metal inthe basin or dam area. A lb. casting poured in 12 seconds, for example,would require a volume for the basin 3 of between about 35 and about 67cubic inches.

The dam area, basin or inoculating area would have a volume on theaverage (1 A seconds dwell time) of about 143 cubic inches for a 500 lb.casting poured in 21 seconds. The exact dwell time required in the damarea is somewhat dependent upon the type of alloy being used, but in anycase, we feel that at least one second is required for effectiveinoculation and that more than two seconds is wasteful of mold space anddetracts from the casting yield obtained. Dwell time is particularlyimportant where the inoculation is done with a nodularizing alloy, whereit is necessary to time the inoculant reaction over the major part ofthe casting cycle. Too long. a dwell time will overinoculate the firstmetal and perhaps under-inoculate the last metal into the mold.

The dam gate area must be held to definite size in order to regulate thespeed of molten metal flow through the system. This is necessary toestablish a base for the dwell time as well as for the rate at whichinoculating alloy will flow into the dam area or basin from the alloyreservoir. In the process of our invention we vary the pouring speed bychanging the darn gate exit area after the dam area. This area is thelimiting or smallest area in the total system and varies according tocasting weight. For castings up to 5,000 pounds in' weight, the dam gateexit area to casting weight is as follows:

TABLE I DAM GATE EXIT AREA 0.17 sq. in.

. in. in. in. in. in.

CASTING WEIGHT For castings above 5000 lbs. in weight we use e ormulaDam gate (in!) [weight (lbs.)]/[ 1.25 V weight (lbs.) X 15.8]

Volume of dam area (ini) [Weight (Lbs.) X 1.5 X 4]/[l.25 V weight(Lbs.)]

An essential feature of our invention is the alloy reservoir, which isused to supply alloy to the dam area during pouring of the casting.

This reservoir comprises a pocket above (FIG. 1) or below (FIG. 3) orprior to (FIG. 4) the dam area or basin. The dam area or basin 3 itselfbecomes a part of the alloy reservoir and excess alloy not contained inthe darn area will be absorbed as the metal flows past the opening tothe alloy reservoir. In some instances the basin itself may contain allof the alloy necessary to treat a given amount of metal.

The size of the dam area is such that its volume will provide at least 1second and preferably 1% or 2 seconds of dwell time, according to thevolume rate of flow of metal.

Another requirement is that maximum surface area of contact is providedbetween the alloy and the flowing metal. This may be done by using a damarea of maximum length and minimum thickness. We have fdund that thelength of the dam gate area should be equal to about one-half inch forevery second of pouring time. A casting being poured in 24 seconds,therefore, would have a dam gate area equal to 12 inches in length. Thedepth of the dam gate area is related normally to the skimming action totrap the products of re action. We like to keep this depth at about 3 to3% inches for castings up to 100 lbs. in weight, at about 4 inches forcastings between 100 and 200 lbs. in weight and at about 4% inches forcastings above 200 lbs. in weight.

Having determined the volume of the dam area related to 1% seconds dwelltime, the length at k inch for each second of pouring time and the depthaccording to the weight range we can easily calculate the width of thedam gate area. This works out at about 1% to 3 inches for most castings.

The reservoir 4 (FIG. 1) comprises a pocket above the dam area generallyequal in size to the dam area or basin but being shorter in length (L).The length being defined as the distance from the inlet end of the damarea to the skimmer 6.

We find that a pocket or reservoir of this configuration will allowuninterrupted flow of the alloy into the metal. The size of the alloy isimportant but, in general, we prefer to use an alloy of about 8 mesh insize or smaller as it is essentially free flowing. The-size of thereservoir, above the point at which it contacts the dam area may be madelarger if necessary in order to hold the total weight of alloy for theweight of the casting to be inoculated.

By providing free flow to the alloy, we find that it enters the metal ata rate equal to the rate of flow of metal from the dam gate.

In practicing our invention we place a piece of polystyrene orconsumable material 11 in the dam area, so that on closing the mold itcovers the opening under the strainer or skimmer 6. We then place therequired weight of alloy in the reservoir and dam area and close it atthe upper end by ramming molding sand in this opening or by closing itwith a sand core. We prefer to close the opening above the alloy,particularly where volatile alloys are being used, so as to prevent anupward flow of gases against the flow of alloy in a downward direction.

The alloy reservoir may be placed above the dame gate (FIG. 1) area orbelow the dam gate area (FIG. 3). In the first case, alloy will flowinto the metal as it is consumed and in the second case metal will flowthrough the alloy and consume it, as it flows through. In some cases thealloy reservoir may also be placed prior to the dam gate area (FIG. 4)as a pocket in the mold.

The consumable material 11 prevents the initial in mshing metal fromcarrying alloy out of the dam area or basin-underneath the strainer. Asthe basin fills the material 11 is destroyed, however, alloy and or slagare normally restrained by the strainer and absorbed alloy and metalpass on to the mold cavity underneath the strainer.

The important feature of the invention is that where the calculated damarea has insufficient volume to hold all of the alloy required, areservoir is supplied of size sufficient to hold the remaining alloy andis so disposed as to supply alloy by solution to the flowing stream ofmolten metal. The primary source of control of alloy flow into themolten metal system is the size of the dam area to give I to 2 secondsof dwell time and the length of this area being about one-half inch oflength per second of pouring time.

While this system works particularly well for the incorporation ofnodularizing alloys into the casting during pouring, we have found thatit works equally well for other types of alloys, such as graphitizinginoculants and even ferro alloys, where it is desired to alter thecomposition of the metal being cast by adding chromium, copper, nickel,manganese and the like, without adding it to all the metal contained inthe pouring alloy.

For certain alloys, such as chromium, which dissolve slowly, it may benecessary to adjust the speed of flow of the metal or increase the dwelltime in the dam gate area by size adjustment, so as to give time foradequate solution.

In an adaptation of our process it is possible to add certain alloys topart of the metal flowing into a mold. This is done by the simpleexpedient of incorporating an additional gating system in the mold, sothat the darn gate of this invention may be bypassed for certain lengthof time during casting. At any desired time the metal may be caused toflow through this dam gate system by a device like a removable plug inthe pouring basin or even by pouring from another ladle. Metal flowingthrough the dam gate system of this invention will then be alloyed whilethat which by-passes this dam gate system will remain unalloyed.

In many castings of complex configuration, particularly those where themolten metal may have to travel a considerable distanceand where it iscustomary to use more than one downsprue and gating system, we prefer toincorporate a plurality of dam gates and alloy reservoirs in the system.Thus, in some cases, the metal from the downsprue may be divided intomore than one channel and each channel would incorporate a dam gatesystem with an alloy reservoir. 'The choice between the use of a singleor a multiple inoculation system is a matter of choice, but in any case,each inoculation system will be designed according to the essentialfeatures already described. In some cases where it is not physicallypossible to use a length of dam area or basin corresponding to one-halfinch for each second of pouring time, we find a shorter length may beused, but we place strips 19 and 21 of consummable polystyrene material(FIG. 5) in the dam area to provide chan' nels 22, 23, 24 for metalflow. The total length of the channels in such a case would be at leastequal to onehalf inch for each second of metal flow.

The working of this invention may be described by a typical example inthis example a nodular cast iron casting of generally uniform sectionand weighing 500 pounds was to be cast using a molten metal that wouldrequire at 2 percent addition of nodularizing alloy to make it nodular.For this purpose a quantity of alloy weighing lbs. and consisting of 50percent, 8 mesh magnesium ferrosilicon, 5 percent rare earth fluoride,percent calcium fluoride and 30 percent calcium silicide, was prepared.

The mold was made entirely in the drag half and a dam gate system havingan exit area of 1.48 inch to pour in 21 seconds, was rammed intoposition between the downsprue and the runner bar to the casting. Theexit area of the dam gate was 10 percent less than the cross-sectionalarea of any other part of the gating system. An alloy reservoir wasrammed in'position in the cope, so that it was immediately above thecenter of the dam area. The dam area itself had a capacity of 144 cubicinches and measured 4 inches wide by 4 inches deep by 9 inches long. Apiece of polystyrene was placed in the dam area ahead of the strainer(as in FIG. 2) and the mold was closed. The 10 lbs. of alloy was placedin the reservoir, which alloy also extended into the basin and sand andwas rammed into the reservoir above the alloy level. The metal was thenpoured into the downsprue, which connected to the darn area and pouringwas substantially complete in 21 seconds.

Substantially no smoke or fume was observed during the pouring and thecasting was found to be completely clean, having a completely nodularstructure when a portion of it was examined under the microscope.

The magnesium content of this portion was found to be 0.037 percent. Tocheck the uniformity of magnesium content an analysis was conducted inthe gating area attached to the casting. This was found to contain 0.038percent magnesium. v 8

While we have described our invention with a certain degree ofparticularity, it is understood that various changes in detail may beresorted to without departing in spirit and scope from the invention asherein claimed.

We claim:

l. A gating system for a mold to provide for alloy additions to moltencast iron'which is poured into the mold including in combination a moldcavity, a downsprue for introducing molten cast iron into the mold, abasin interposed between said mold cavity and said downsprue and beingfluidly connected to said downsprue, said basin adapted to receive alloywhich is to be added to molten cast iron, a consumable plastic memberlocated in said basin and closing the exit end thereof until consumed bythe .action of the molten cast iron thereon, a skimmer located in saidbasin, passageway means fluidly connecting said basin to said moldcavity, a. restriction in said passageway means comprising the smallestcross sectional flow area in the gating system and determining the dwelltime of molten cast iron in said basin during a pouring cycle, the crosssectional area of said restriction being related to the casting weightas set forth as follows:

and being of such a size that the dwell time of the molten cast iron insaid basin is between about 1 and 2 seconds, the volume of said basinbeing determined by the following formula:

V (in?) [Wgt. (lbs.) D.T. (Dwell Time in seconds) X 4]/[l.25 V weight(lbs.

2. A gating systemas claimed in claim I, wherein an alloy reservoir islocated above said basin and comm unicates directly therewith.

'3. A gating system as claimed in claim 1, wherein an each second ofpouring time infilling the mold cavity.

6. A gating system'as claimed in claim 1 wherein at least one lengthwisepartition of consumable plastic material is placed in said basin toproduce a plurality of'flow channels through aid basin.

7. A gating system for a mold to provide for additions to molten castiron which is poured into the mold including in combination a moldcavity, a downsprue for introducing molten cast iron into'the mold, abasin interposed between said mold cavity and said downsprue andbeingfluidly connected to downsprue, at least one partition of consumablematerial positioned in said basin to produce a plurality of flowchannels through said basin, a consumable member located in said basinand closing the exit end thereof, passageway means fluidly connectingsaid basin' to said mold cavity, a restriction insaid passagewaymeans-comprising the smallest cross sectional flow area in the gatingsystem and deter mining the dwell time of molten castiron in said basinduring a pouring cycle, the cross'sectional area of said restrictionbeing related to forth as follows: V

the casting weight as set (Dwell Time in seconds) 1 1 s q 1 v a: r

CASTING WEIGHT DAM GATE EXIT AREA 10 1 0.17 sq. in. 20 1 0.28 s in. 300.32 s 40 0.46 sq. in. 0.55 sq. in. I 0.65 .sq. in. 0.72 s 111.. 0.8lsq. in. 0.90 sq. in. 115 0.98 sq. in. 200v 1.06 sq. in. 250 l.l5.sq. in.300 L24 sq. in. 350 1.32 sq. in. 400. 1.40 sq. in. 500 1.48 sq. in. 600L56 sq. in.

700 1.72 sq. in. v 800 L87 sq. in. 900 2.03 sqJin. 1000 2.18 sq. in.1250 2.4] sq. in. I500 2.64 sq. in. 1750 2.85 sq. in. 2000 3.06 sq. in.2500' 3.35 sq. in. 3000 3.70 sq. in. 4000 4.20 sq. in.

. 5000 4.00 sq. in.

and being of such a size that the dwell time of molten cast iron in saidbasin is between about 1 and 2 seconds, the volume of said basin beingdetermined by the following formula: cl V (in.) =.[Wgt.'(lbs.) X D.T.

in. s

1. A gating system for a mold to provide for alloy additions to moltencast iron which is poured into the mold including in combination a moldcavity, a downsprue for introducing molten cast iron into the mold, abasin interposed between said mold cavity and said downsprue and beingfluidly connected to said downsprue, said basin adapted to receive alloywhich is to be added to molten cast iron, a consumable plastic memberlocated in said basin and closing the exit end thereof until consumed bythe action of the molten cast iron thereon, a skimmer located in saidbasin, passageway means fluidly connecting said basin to said moldcavity, a restriction in said passageway means comprising the smallestcross sectional flow area in the gating system and determining the dwelltime of molten cast iron in said basin during a pouring cycle, the crosssectional area of said restriction being related to the casting weightas set forth as follows: CASTING WEIGHT DAM GATE EXIT AREA 10 0.17 sq.in. 20 0.28 sq. in. 30 0.32 sq. in. 40 0.46 sq. In. 50 0.55 sq. in. 750.65 sq. in. 100 0.72 sq. in. 125 0.81 sq. in. 150 0.90 sq. in. 175 0.98sq. in. 200 1.06 sq. in. 250 1.15 sq. in. 300 1.24 sq. in. 350 1.32 sq.in. 400 1.40 sq. in. 500 1.48 sq. in. 600 1.56 sq. in. 700 1.72 sq in.800 1.87 sq. in. 900 2.03 sq. in. 1000 2.18 sq. in. 1250 2.41 sq. in.1500 2.64 sq. in. 1750 2.85 sq. in. 2000 3.06 sq. in. 2500 3.35 sq. in.3000 3.70 sq. in. 4000 4.20 sq. in. 5000 4.60 sq. in. and being of sucha size that the dwell time of the molten cast iron in said basin isbetween about 1 and 2 seconds, the volume of said basin being determinedby the following formula: V (in.3) (Wgt. (lbs.) X D.T. (Dwell Time inseconds) X 4)/(1.25 square root weight (lbs.))
 2. A gating system asclaimed in claim 1, wherein an alloy reservoir is located above saidbasin and communicates directly therewith.
 3. A gating system as claimedin claim 1, wherein an alloy reservoir is located below said basin andcommunicates directly therewith.
 4. A gating system as claimed in claim1, wherein an alloy reservoir is located upstream of said basin.
 5. Agating system as claimed in claim 1, wherein the length of said basin ison the order of one-half inch for each second of pouring time in fillingthe mold cavity.
 6. A gating system as claimed in claim 1, wherein atleast one lengthwise partition of consumable plastic material is placedin said basin to produce a plurality of flow channels through aid basin.7. A gating system for a mold to provide for additions to molten castiron which is poured into the mold including in combination a moldcavity, a downsprue for introducing molten cast iron into the mold, abasin interposed between said mold cavity and said downsprue and beingfluidly connected to said downsprue, at least one partition ofconsumable material positioned in said basin to produce a plurality offlow channels through said basin, a consumable member located in saidbasin and closing the exit end thereof, passageway means fluidlyconnecting said basin to said mold cavity, a restriction in saidpassageway means comprising the smallest cross sectional flow area inthe gating system and determining the dwell time of molten cast iron insaid basin during a pouring cycle, the cross sectional area of saidrestriction being related to the casting weight as set forth as follows:CASTING WEIGHT DAM GATE EXIT AREA 10 0.17 sq. in. 20 0.28 sq. in. 300.32 sq. in. 40 0.46 sq. in. 50 0.55 sq. in. 75 0.65 sq. in. 100 0.72sq. in. 125 0.81 sq. in. 150 0.90 sq. in. 175 0.98 sq. in. 200 1.06 sq.in. 250 1.15 sq. in. 300 1.24 sq. in. 350 1.32 sq. in. 400 1.40 sq. in.500 1.48 sq. in. 600 1.56 sq. in. 700 1.72 sq. in. 800 1.87 sq. in. 9002.03 sq. in. 1000 2.18 sq. in. 1250 2.41 sq. in. 1500 2.64 sq. in. 17502.85 sq. in. 2000 3.06 sq. in. 2500 3.35 sq. in. 3000 3.70 sq. in. 40004.20 sq. in. 5000 4.60 sq. in. and being of such a size that the dwelltime of molten cast iron in said basin is between about 1 and 2 seconds,the volume of said basin Being determined by the following formula: cl V(in.3) (Wgt. (lbs.) X D.T. (Dwell Time in seconds) X 4)/(1.25 SquareRoot weight (lbs.))